CO67-186μm谱线在天体物理研究中的作用  

THE ROLE OF CO 67-186 μm LINES IN ASTROPHYSICS

作　　者：毛瑞青[1] 曾琴[1] 陈亚峰 裴春传[1] 缪源[2] 

机构地区：[1]中国科学院紫金山天文台 [2]南京大学物理系,南京210093

出　　处：《天文学报》1999年第4期376-381,共6页Acta Astronomica Sinica

摘　　要：采用球型大速度梯度模型，对ＩＲＣ＋ １０２１６ 、ＡＦＧＬ２６８８ 和ＮＧＣ７０２７ 等经ＩＳＯ 发表的首次数据证明有相对强的ＣＯ６７ － １８６ μｍ 发射线的天体作模型计算．统计平衡辐射转移计算共覆盖低于能量４８６３ ｃｍ －１（ｖ ＝ ０ ，Ｊ＝ ０ 能级的能量为０） 的全部能级，即ｖ ＝ ０ 、Ｊ＝ ０ －５０ ，ｖ ＝ １ 、Ｊ＝ ０ － ３７ 和ｖ ＝ ２ 、Ｊ＝ ０ － １７ 的１０７ 个能级．计算表明ＣＯ 谱线的流量相对值对于上能级转动量子数Ｊｕ 的分布函数，是该谱线发射区物理条件的良好探针．ＩＲＣ＋ １０２１６ 的ＣＯ远红外发射线主要由中央星激发形成，而ＡＦＧＬ２６８８ 和ＮＧＣ７０２７ 区则是因温暖和致密的冲击气体所致．对ＩＳＯ 首次数据涉及的其他天体的ＣＯ 谱线激发机制，也作了一些讨论。ＣＯ 的谱线是在６７ － １８６ μｍ 波段探测动能温度数百度以上的热天体，诸如富碳、富氧演化星包层，行星状星云。A spherical and large velocity gradient model is adopted for the theoretical calculations of NGC7027, AFGL2688 and IRC+10216, whose emissions of CO far infrared lines are comparatively strong. The statistical equilibrium calculations cover 107 energy levels. The upper energy limit is 4863 cm -1 above the energy level with v=0 and J=0. There are altogether 107 energy levels with v=0, J=0-50; v=1,J=0-37 and v=2, J=0-17 . The relative flux distributions of the CO lines, as functions of the upper rotational quantum number J u of the line, may be a good probe to examine the physical conditions of the region in which the CO line emissions arise. The CO far infrared lines of IRC+10216 are excited mainly by the central star, while for NGC7027 and AFGL2688 by the shocked warm and dense gases. The excitation mechanism is also discussed for other observed objects by using ISO. The CO spectra in the wavelength range 67-186 μm are important probes for detecting the objects with kinetic temperatures of several hundred degrees, i.e.the envelopes of carbon or oxygen rich stars, planetary nebulae, young stellar objects and star forming complexes.

关 键 词：谱线形成 红外辐射 星际介质 天体物理 

分 类 号：P14[天文地球—天体物理]